1. Field of the Invention
The present invention relates to a honeycomb filter and a method of manufacturing the same. More particularly, the present invention relates to a honeycomb filter which may be suitably used as a filter for purifying exhaust gas discharged from diesel engines, and a method of manufacturing the same.
2. Description of Related Art
It is necessary to remove particulate matter and toxic substances (hereinafter may be collectively called “PM”) from exhaust gas discharged from internal combustion engines, boilers, or the like, taking environmental effects into consideration. In particular, regulations concerning removal of particulate matter discharged from diesel engines have been tightened in Europe, the USA, and Japan. As a diesel particulate filter (hereinafter may be called “DPF”) for removing PM, a honeycomb filter has attracted attention.
As shown in FIG. 5, a honeycomb filter generally includes porous partition walls 2 forming a plurality of cells 3 extending in one direction, and plugging sections 4 alternately plugging the cells 3 at ends 42 and 44. In a honeycomb filter 1 configured as shown in FIG. 5, a fluid flows into the cells 3 through inflow openings (e.g. cell openings at the end 42), passes through the partition walls 2, and is discharged from the adjacent cells 3. In this case, the partition walls 2 serve as a filter so that PM is deposited on the partition walls 2.
Since the pressure loss is increased along with deposition of PM on the partition walls, it is necessary to remove such deposited substances. For example, a DPF has been developed in which a catalyst is supported on the partition walls in order to assist burning and removal of PM deposited on the partition walls. A method of continuously burning and removing PM by utilizing an increase in exhaust gas temperature has also been proposed. In another method, mechanical impact is applied to the surfaces of the partition walls of the honeycomb filter to increase the number of pores in the surface area. This increases the contact area between the catalyst supported on the partition walls of the honeycomb structure and PM deposited on the partition walls to increase the oxidation performance (see patent document 1, for example).
[Patent document 1] JP-A-2002-355511